#include "petscksp.h"
/*
A={1 2 3 4 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0;
   0 0 0 0 0 0
}
*/
int main(int argc, char ** argv)
{
    Mat A;
    int m,n;
    static int d_nnz[4]={1,1,1,1},o_nnz[4]={1,1,1,1};// 1-room for diagonal entry
    int rank;
    PetscInitialize( &argc, &argv, 0, 0 );
    MPI_Comm_rank(PETSC_COMM_WORLD,&rank);
    if(rank==0)// rank=0
    {
	d_nnz[0]=4;
    }
    MatCreateMPIAIJ(PETSC_COMM_WORLD,PETSC_DECIDE,PETSC_DECIDE,
	    8,6,PETSC_DEFAULT,d_nnz ,PETSC_DEFAULT, o_nnz, &A);
    MatGetLocalSize(A,&m,&n);
    printf("m=%d,n=%d\n",m,n);
    MatSetValue(A,0,0,1,INSERT_VALUES);
    MatSetValue(A,0,1,2,INSERT_VALUES);
    MatSetValue(A,0,2,3,INSERT_VALUES);
    MatSetValue(A,0,3,4,INSERT_VALUES);
    MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);
    MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);
    MatView(A,PETSC_VIEWER_STDOUT_WORLD);
    MatDestroy( A );
    PetscFinalize( );
    return 0;
}